Expression dynamics and antiviral role of chicken OASL during infectious bronchitis virus infection.

OASL, a distinctive member of the 2'-5'-oligoadenylate synthetase (OAS) family, is a well-characterized interferon-stimulated gene (ISG). In mammals and certain avian species, OASL exhibits dual functions in antiviral defense and innate immune regulation. However, the biological role of chicken OASL (chOASL) remains poorly understood, largely due to the natural absence of RIG-I in chickens. Infectious bronchitis virus (IBV) belongs to Gammacoronavirus genus and causes substantial economic losses in the global poultry industry. To explore whether chOASL is involved in the host defense against IBV, this study aimed to comprehensively characterize its expression dynamics and antiviral function. Firstly, the anti-chOASL polyclonal antibody was generated using prokaryotically expressed recombinant protein. Using this validated tool, we demonstrated that endogenous chOASL was significantly induced by Poly(I:C) and QX-IBV in various chicken cells. Furthermore, we mapped the baseline tissue distribution of chOASL protein for the first time and proved that chOASL was markedly upregulated, particularly in immune organs and IBV target tissues during IBV infection. Importantly, overexpression and knockdown assays verified that chOASL could suppress IBV replication. In conclusion, this study not only provides a reliable tool for detecting chOASL but also establishes its specific expression profile and direct antiviral activity against IBV, laying a solid foundation for further elucidating antiviral mechanisms of chOASL.